In response to Microsoft releasing Internet Explorer 7, Mozilla has released Firefox v2.0. You can download the English version of FF2 for Windows at http://www.mozilla.com/products/download.html?product=firefox-2.0&os=win&lang=en-US.
I haven't installed this yet. I may actually do a completely clean/fresh install of FF2 (just because I haven't done a clean install in a long time of Firefox) and then just migrate my settings over.